How do I edit a file after I shell to a Docker container

Question

I successfully shelled to a Docker container using   docker exec -i -t 69f1711a205e bash   Now I need to edit file and I don t have any editors inside   root 69f1711a205e    nano bash  nano  command not found root 69f1711a205e    pico bash  pico  command not found root 69f1711a205e    vi bash  vi  command not found root 69f1711a205e    vim bash  vim  command not found root 69f1711a205e    emacs bash  emacs  command not found root 69f1711a205e      How do I edit files

User · Answer

For common edit operations I prefer to install vi (vim-tiny), which uses only 1491 kB or nano which uses 1707 kB.

In other hand vim uses 28.9 MB.

We have to remember that in order for apt-get install to work, we have to do the update the first time, so:

apt-get update
apt-get install vim-tiny

To start the editor in CLI we need to enter vi.

User · Answer

As in the comments  there s no default editor set - strange - the  EDITOR environment variable is empty  You can log in into a container with   docker exec -it  lt container gt  bash   And run   apt-get update apt-get install vim   Or use the following Dockerfile   FROM  confluent postgres-bw 0 1  RUN   apt-get    update   RUN   apt-get    install    -y    vim     Docker images are delivered trimmed to the bare minimum - so no editor is installed with the shipped container  That s why there s a need to install it manually   EDIT  I also encourage you read my post about the topic

User · Answer

It is kind of screwy  but in a pinch you can use sed or awk to make small edits or remove text  Be careful with your regex targets of course and be aware that you re likely root on your container and might have to re-adjust permissions   For example  removing a full line that contains text matching a regex   awk    targetText   file txt  gt  temp  amp  amp  mv temp file txt    More

User · Answer

You can just edit your file on host and quickly copy it into and run it inside the container  Here is my one-line shortcut to copy and run a Python file   docker cp main py my-container  data scripts    docker exec -it my-container python  data scripts main py

User · Answer

To keep your Docker images small  don t install unnecessary editors  You can edit the files over SSH from the Docker host to the container   vim scp   remoteuser containerip  path to document

User · Answer

See Stack Overflow question sed edit file in place  It would be a good option here  if    To modify a large file  it s impossible to use cat  Install Vim is not allowed or takes too long  My situation is using the MySQL 5 7 image when I want to change the my cnf file  there is no vim  vi  and Vim install takes too long  China Great Firewall   sed is provided in the image  and it s quite simple  My usage is like  sed -i  s testtobechanged textwanted g filename    Use man sed or look for other tutorials for more complex usage

User · Answer

An easy way to edit a few lines would be   echo  deb http   deb debian org debian stretch main   gt  sources list

User · Answer

You can open existing file with   cat filename extension   and copy all the existing text on clipboard    Then delete old file with   rm filename extension   or rename old file with   mv old-filename extension new-filename extension   Create new file with   cat  gt  new-file extension   Then paste all text copied on clipboard  press Enter and exit with save by pressing ctrl z  And voila no need to install any kind of editors

User · Answer

Sometime you must first run the container with root   docker exec -ti --user root  lt container-id gt   bin bash   Then in the container  to install Vim or something else   apt-get install vim

User · Answer

You can also use a special container which will contain only the command you need  Vim  I chose python-vim  It assumes that the data you want to edit are in a data container built with the following Dockerfile   FROM debian jessie ENV MY USER PASS my user pass RUN groupadd --gid 1001 my user RUN useradd -ms  bin bash --home  home my user               -p   echo  print crypt    MY USER PASS -password     salt      perl                --uid 1001 --gid 1001 my user ADD src  home my user src RUN chown -R my user my user  home my user src RUN chmod u x  home my user src CMD   true     You will be able to edit your data by mounting a Docker volume  src volume  which will be shared by your data container  src data  and the python-vim container   docker volume create --name src volume docker build -t src data   docker run -d -v src volume  home my user src --name src data 1 src data docker run --rm -it -v src volume  src fedeg python-vim latest   That way  you do not change your containers  You just use a special container for this work

User · Answer

You can use cat if installed  with the  gt  caracter  Here is the manipulation    cat  gt  file to edit  1 Write or Paste you text  2 don t forget to leave a blank line at the end of file  3 Ctrl   C to apply configuration   Now you can see the result with the command  cat file

User · Answer

After you shelled to the Docker container  just type   apt-get update apt-get install nano

User · Answer

If you use Windows container and you want change any file  you can get and use Vim in Powershell console easily   To shelled to the Windows Docker container with PowerShell   docker exec -it  lt name gt  powershell   First install Chocolatey package manager   Invoke-WebRequest https   chocolatey org install ps1 -UseBasicParsing   Invoke-Expression  Install Vim  choco install vim Refresh ENVIRONMENTAL VARIABLE You can just exit and shell back to the container Go to file location and Vim it vim file txt

User · Answer

You can use cat if it s installed  which will most likely be the case if it s not a bare raw container  It works in a pinch  and ok when copy pasting to a proper editor locally   cat  gt  file   1  type in your content   2  leave a newline at end of file   3  ctrl-c    better  ctrl-d  cat file   cat will output each line on receiving a newline  Make sure to add a newline for that last line  ctrl-c sends a SIGINT for cat to exit gracefully  From the comments you see that you can also hit ctrl-d to denote end-of-file   no more input coming     Another option is something like infilter which injects a process into the container namespace with some ptrace magic  https   github com yadutaf infilter

User · Answer

I use  docker run   not  docker exec    and I m in a restricted zone where we cannot install an editor  But I have an editor on the Docker host    My workaround is  Bind mount a volume from the Docker host to the container  https   docs docker com engine reference run   volume-shared-filesystems   and edit the file outside the container  It looks like this   docker run -v  outside dir  container dir   This is mostly for experimenting  and later I d change the file when building the image

User · Answer

If you don t want to add an editor just to make a few small changes  e g   change the Tomcat configuration   you can just use   docker cp  lt container gt   path to file ext     which copies it to your local machine  to your current directory   Then edit the file locally using your favorite editor  and then do a  docker cp file ext  lt container gt   path to file ext   to replace the old file

[docker] How do I edit a file after I shell to a Docker container?

Examples related to docker